Yu Wang, Zhuo-Ling Xie, Zhao-Lin Zeng, Cheng-Cheng Li, Jia-Hui An, Qing-Qing Hao, Hui-Bin Ge, Hui-Yong Chen, Xiao-Xun Ma, Qun-Xing Luo
{"title":"ZnAl2O4 Spinel 上水杨酸甲酯综合催化氨解和脱水的动力学和机理","authors":"Yu Wang, Zhuo-Ling Xie, Zhao-Lin Zeng, Cheng-Cheng Li, Jia-Hui An, Qing-Qing Hao, Hui-Bin Ge, Hui-Yong Chen, Xiao-Xun Ma, Qun-Xing Luo","doi":"10.1021/acscatal.4c01477","DOIUrl":null,"url":null,"abstract":"A kinetic and mechanistic study of direct catalytic nitrilation from methyl salicylate and ammonia is conducted by using an amphoteric ZnAl<sub>2</sub>O<sub>4</sub> spinel as a model catalyst. This overall process integrates the catalytic ammonolysis of esters with the dehydration of amides, proceeding stepwise over the concerted Lewis acid–base pairs of Zn–O–Al linkages. The chemisorption and activation of C–O bonds of the ester over Lewis acid–base pairs facilitate the leaving of the methoxy group, while Lewis basic oxygen (Zn–O*–Al) serves as the main hub station for multistep proton transportation, thus leading to the decreased apparent activation energy of nitrilation and ammonolysis. The combined experimental and computational evidence confirms that this direct nitrilation process follows a monomolecular surface adsorption model, <i>i.e.</i>, the Eley–Rideal mechanism, involving eight elementary reaction steps in which chemisorbed surface species of methyl salicylate react with gaseous NH<sub>3</sub> molecules <i>via</i> nucleophilic addition–elimination and multistep proton transfer to generate amides and nitriles in sequence. Microkinetic model discrimination and DFT calculations reveal that the formation of chemisorbed imine (C═N–H) <i>via</i> proton transfer from the Lewis basic oxygen atom (Zn–O*–Al) to the carbonyl oxygen (C═O*) is the rate-determining step, thereby providing a potential consideration of protonation and deprotonation ability to rationally design an improved catalyst.","PeriodicalId":9,"journal":{"name":"ACS Catalysis ","volume":null,"pages":null},"PeriodicalIF":11.3000,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Kinetics and Mechanism of Integrated Catalytic Ammonolysis and Dehydration from Methyl Salicylate over ZnAl2O4 Spinel\",\"authors\":\"Yu Wang, Zhuo-Ling Xie, Zhao-Lin Zeng, Cheng-Cheng Li, Jia-Hui An, Qing-Qing Hao, Hui-Bin Ge, Hui-Yong Chen, Xiao-Xun Ma, Qun-Xing Luo\",\"doi\":\"10.1021/acscatal.4c01477\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"A kinetic and mechanistic study of direct catalytic nitrilation from methyl salicylate and ammonia is conducted by using an amphoteric ZnAl<sub>2</sub>O<sub>4</sub> spinel as a model catalyst. This overall process integrates the catalytic ammonolysis of esters with the dehydration of amides, proceeding stepwise over the concerted Lewis acid–base pairs of Zn–O–Al linkages. The chemisorption and activation of C–O bonds of the ester over Lewis acid–base pairs facilitate the leaving of the methoxy group, while Lewis basic oxygen (Zn–O*–Al) serves as the main hub station for multistep proton transportation, thus leading to the decreased apparent activation energy of nitrilation and ammonolysis. The combined experimental and computational evidence confirms that this direct nitrilation process follows a monomolecular surface adsorption model, <i>i.e.</i>, the Eley–Rideal mechanism, involving eight elementary reaction steps in which chemisorbed surface species of methyl salicylate react with gaseous NH<sub>3</sub> molecules <i>via</i> nucleophilic addition–elimination and multistep proton transfer to generate amides and nitriles in sequence. 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Kinetics and Mechanism of Integrated Catalytic Ammonolysis and Dehydration from Methyl Salicylate over ZnAl2O4 Spinel
A kinetic and mechanistic study of direct catalytic nitrilation from methyl salicylate and ammonia is conducted by using an amphoteric ZnAl2O4 spinel as a model catalyst. This overall process integrates the catalytic ammonolysis of esters with the dehydration of amides, proceeding stepwise over the concerted Lewis acid–base pairs of Zn–O–Al linkages. The chemisorption and activation of C–O bonds of the ester over Lewis acid–base pairs facilitate the leaving of the methoxy group, while Lewis basic oxygen (Zn–O*–Al) serves as the main hub station for multistep proton transportation, thus leading to the decreased apparent activation energy of nitrilation and ammonolysis. The combined experimental and computational evidence confirms that this direct nitrilation process follows a monomolecular surface adsorption model, i.e., the Eley–Rideal mechanism, involving eight elementary reaction steps in which chemisorbed surface species of methyl salicylate react with gaseous NH3 molecules via nucleophilic addition–elimination and multistep proton transfer to generate amides and nitriles in sequence. Microkinetic model discrimination and DFT calculations reveal that the formation of chemisorbed imine (C═N–H) via proton transfer from the Lewis basic oxygen atom (Zn–O*–Al) to the carbonyl oxygen (C═O*) is the rate-determining step, thereby providing a potential consideration of protonation and deprotonation ability to rationally design an improved catalyst.
期刊介绍:
ACS Catalysis is an esteemed journal that publishes original research in the fields of heterogeneous catalysis, molecular catalysis, and biocatalysis. It offers broad coverage across diverse areas such as life sciences, organometallics and synthesis, photochemistry and electrochemistry, drug discovery and synthesis, materials science, environmental protection, polymer discovery and synthesis, and energy and fuels.
The scope of the journal is to showcase innovative work in various aspects of catalysis. This includes new reactions and novel synthetic approaches utilizing known catalysts, the discovery or modification of new catalysts, elucidation of catalytic mechanisms through cutting-edge investigations, practical enhancements of existing processes, as well as conceptual advances in the field. Contributions to ACS Catalysis can encompass both experimental and theoretical research focused on catalytic molecules, macromolecules, and materials that exhibit catalytic turnover.